Coffee maker and microwave oven and method for controlling the same

ABSTRACT

Coffee maker and microwave oven and method for controlling the same are disclosed. 
     The coffee maker and microwave oven includes an outfit room for mounting various electric components on an inside thereof, a case at one side of the outfit room, a water tank in the case, a funnel having a filter placed thereon for extraction of coffee, a jug under the funnel for storage of extracted coffee, a water supply pipe having one end connected to the water tank, the other end position over the funnel, and a portion on a bottom of the case, and a heater assembly on the bottom of the case, the heater assembly having a heating heater for heating potable water passing through the water supply pipe, and a heat conservation heater for heating coffee in the jug to maintain a temperature of the coffee constant.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of Korean Application Nos.P2003-86718, filed on Dec. 2, 2003, P2003-87239 and P2003-87240, bothfiled on Dec. 3, 2003, and P2004-11914 and P2004-11830, both filed onFeb. 23, 2004, which are hereby incorporated by reference as if fullyset forth herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to coffee maker and microwave ovens, andmore particularly, to a coffee maker and microwave oven and a method forcontrolling the same which has a coffee extraction function.

2. Discussion of the Related Art

In general, a microwave oven cooks food with intermolecular frictionalheat generated as a high frequency wave (about 2,450 MHz) disturbsmolecular arrangement of the food.

Because the microwave oven heats the food with the high frequency wave,the microwave oven cannot cook various kinds of food. For an example,coffee, people enjoys to drink, cannot be prepared with the microwaveoven, to require a coffee maker, separately.

However, presently, as a city grows the denser, leading to have a smallresidential space, and according to the trend of pursuing practicality,the various necessaries of life, starting from home appliances, arerequired to be compact, such that the home appliances are required tohave, not only the traditional original functions, but also variousextra functions.

However, the related art microwave oven cannot meet such consumerdemands.

SUMMARY OF THE INVENTION

Accordingly, the present invention is directed to a coffee maker andmicrowave oven and a method for controlling the same that substantiallyobviates one or more problems due to limitations and disadvantages ofthe related art.

An object of the present invention is to provide a coffee maker andmicrowave oven and a method for controlling the same which have a coffeeextraction function.

Additional advantages, objects, and features of the invention will beset forth in part in the description which follows and in part willbecome apparent to those having ordinary skill in the art uponexamination of the following or may be learned from practice of theinvention. The objectives and other advantages of the invention may berealized and attained by the structure particularly pointed out in thewritten description and claims hereof as well as the appended drawings.

To achieve these objects and other advantages and in accordance with thepurpose of the invention, as embodied and broadly described herein, acoffee maker and microwave oven includes an outfit room for mountingvarious electric components on an inside thereof, a case at one side ofthe outfit room, a water tank in the case, a funnel having a filterplaced thereon for extraction of coffee, a jug under the funnel forstorage of extracted coffee, a water supply pipe having one endconnected to the water tank, the other end position over the funnel, anda portion on a bottom of the case, and a heater assembly on the bottomof the case, the heater assembly having a heating heater for heatingpotable water passing through the water supply pipe, and a heatconservation heater for heating coffee in the jug to maintain atemperature of the coffee constant.

The heater assembly further includes a heater tube in contact with thewater supply pipe on the bottom of the case, having the heating heaterand the heat conservation heater mounted therein.

The heating heater includes a heating wire with a 750 W powerconsumption, and the heat conservation heater includes a heating wirewith a 90 W power consumption.

The heating heater has a fixed gap to the heat conservation heater, andthe heating heater is wound around an axis of the heater tube in ahelix, and the heat conservation heater is wound along an insidecircumferential surface of the heater tube in a helix.

The heating heater and the heat conservation heater include insulatingportion at both ends respectively, for preventing short circuit. Theinsulating portion of the heating heater is longer than the insulatingportion of the heat conservation heater.

The coffee maker and microwave oven further includes a temperaturesensor on an outside surface of the heater tube for measuring atemperature of the heating heater. Preferably, the temperature sensorincludes a thermistor of which internal resistance varies with atemperature.

The funnel is at a center of an inside of the water tank, and the waterpipe includes a shower head at the other end thereof over the funnel forspraying potable water into an inside of the funnel.

The heater assembly further includes a heater tube in contact with aportion of the water supply pipe on the bottom of the case, the heatertube having the heating heater provided therein.

The heating heater includes first terminals at both ends respectivelyconnected to a coil for supplying power, and the heating heater includesa sheath heater.

The heat conservation heater is positioned opposite to the heatingheater with respect to a portion of the water supply tube on the bottomof the case.

The heat conservation heater includes a plate heater in close contactwith an underside of the case.

The heat conservation heater includes a second terminal on one side ofan underside thereof connected to a coil for supplying power thereto,and the heat conservation heater is enclosed with a metal plate having agood thermal conductivity excluding a portion having the second terminalformed thereon.

The coffee maker and microwave oven further includes a heat conductionplate on an underside of the case for effective transmission of heatfrom the heat conservation heater to the jug, and the heat conservationheater is in close contact with an underside surface of the heatconduction plate.

The case further includes a door panel on a front of the case, having aportion positioned below the heat conservation heater, and the heatconservation heater includes a shielding plate on an underside of theheat conservation heater for preventing transmission of heat from theheat conservation heater to the door panel.

The second terminal includes at least two conductive wires wound aroundthe second terminal and connected to the coil, and the connectionportion of the conductive wires and the coil further includes aninsulating tube.

In another aspect of the present invention, a method for controlling acoffee maker and microwave oven, includes the steps of supplying potablewater to a funnel through a water supply pipe, and putting a heatingheater into operation for heating the potable water, upon reception of acoffee extraction order, extracting coffee at the funnel, counting anoperation time period of the heating heater, comparing the operationtime period of the heating heater to a preset time period, and stoppingthe heating heater, and putting a heat conservation heater intooperation for conservation of a temperature of the extracted coffee, ifthe operation time period of the heating heater exceeds the preset timeperiod.

The preset time period is determined by a test as a maximum time periodrequired for extraction of coffee.

In another aspect of the present invention, a method for controlling acoffee marker and microwave oven, includes the steps of supplyingpotable water to a funnel through a water supply pipe, and putting aheating heater into operation for heating the potable water, uponreception of a coffee extraction order, measuring a temperature of theheating heater by using a temperature sensor, receiving the measuretemperature periodically, and calculating a rate of temperature changeof the heating heater, determining whether the rate of temperaturechange is lower than a preset value or not, and putting a heatconservation heater into operation such that the heat conservationheater is in operation together with the heating heater for extractingcoffee, if the rate of temperature change lower than the preset value.

The rate of temperature change of the heater is calculated according tothe following equation.ΔT=(T _(n) −T _(n−1))/(t _(n) −t _(n−1))

Where, ΔT denotes a rate of temperature change of the heater, T_(n)denotes the heater temperature measured at a t_(n) time, and T_(n−1)denotes the heater temperature measured at a t_(n−1) time.

The method further includes the steps of determining whether the coffeeextraction is finished or not, and, if the coffee extraction isfinished, stopping the heating heater, to operate the heat conservationheater only, for conservation of the temperature of the extractedcoffee.

In further aspect of the present invention, a method for controlling acoffee maker and microwave oven, includes the steps of supplying potablewater to a funnel through a water supply pipe, and putting a heatingheater into operation for heating the potable water, upon reception of acoffee extraction order, extracting coffee at the funnel, upon finishingextraction of coffee, operating a heat conservation heater for a presetheat conservation time period, to conserve a heat of the extractedcoffee, stopping the heat conservation heater if the heat conservationtime period is passed, and upon reception of a coffee heat conservationorder, the heat conservation heater being put into operation, forcarrying out heat conservation of the coffee, again.

The step of operating a heat conservation heater includes the steps ofmeasuring a temperature of the heating heater with a temperature sensor,receiving the measured temperature periodically, and calculating a rateof temperature change of the heating heater, comparing the rate oftemperature change to a preset value, and if the rate of temperaturechange exceeds the preset value, stopping the heating heater, andputting the heat conservation heater into operation.

The rate of temperature change of the heater is calculated according tothe following equation.ΔT=(T _(n) −T _(n−1))/(t _(n) −t _(n−1))

Where, ΔT denotes a rate of temperature change of the heater, T_(n)denotes the heater temperature measured at a t_(n) time, and T_(n−1)denotes the heater temperature measured at a t_(n−1) time.

The step of the heat conservation heater being put into operationincludes the steps of determining whether the coffee heat conservationorder is received or not, and, if the coffee heat conservation order isreceived, putting only the heat conservation heater into operation, forconservation of heat of the coffee, again.

It is to be understood that both the foregoing general description andthe following detailed description of the present invention areexemplary and explanatory and are intended to provide furtherexplanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this application, illustrate embodiment(s) of the invention andtogether with the description serve to explain the principle of theinvention. In the drawings;

FIG. 1 illustrates a section of a coffee maker and microwave oven inaccordance with a first preferred embodiment of the present invention;

FIG. 2 illustrates a bottom perspective view of a coffee maker unit inFIG. 1;

FIG. 3 illustrates a perspective view of a heater assembly in accordancewith a first preferred embodiment of the present invention;

FIG. 4 illustrates a diagram showing detail of a heating heater and aheat conservation heater;

FIG. 5 illustrates a perspective view of a coffee maker and microwaveoven in accordance with a second preferred embodiment of the presentinvention;

FIG. 6 illustrates a section of a coffee maker and microwave oven inaccordance with a third preferred embodiment of the present invention;

FIG. 7 illustrates a perspective view of a coffee maker and microwaveoven in accordance with a third preferred embodiment of the presentinvention;

FIG. 8 illustrates a bottom view of a coffee maker and microwave oven inaccordance with a third preferred embodiment of the present invention;

FIG. 9 illustrates a partial side section of a coffee maker andmicrowave oven in accordance with a third preferred embodiment of thepresent invention;

FIG. 10 illustrates a flow chart showing the steps of a method forcontrolling a coffee maker and microwave oven in accordance with afourth preferred embodiment of the present invention;

FIG. 11 illustrates a flow chart showing the steps of a method forcontrolling a coffee maker and microwave oven in accordance with a fifthpreferred embodiment of the present invention; and

FIG. 12 illustrates a flow chart showing the steps of a method forcontrolling a coffee maker and microwave oven in accordance with a sixthpreferred embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to the preferred embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings. Wherever possible, the same reference numbers will be usedthroughout the drawings to refer to the same or like parts.

FIG. 1 illustrates a section of a coffee maker and microwave oven inaccordance with a first preferred embodiment of the present invention,and FIG. 2 illustrates a bottom perspective view of a coffee maker unitin the coffee maker and microwave oven in FIG. 1.

Referring to FIGS. 1 and 2, the coffee maker and microwave oven includesa cabinet 100 forming an exterior, an outfit room 120 in the cabinet100, and a coffee maker unit at one side of the outfit room 120.

In the outfit room 120, there are various electric parts, such as amagnetron 121, a high voltage transformer 122, and a convection fan 123.The magnetron 121 receives an external high voltage power, and generatesa microwave, and the high voltage transformer 122 transforms externalpower to high voltage power, before application to the magnetron 121.The convection fan 123 cools down various components in the outfit room120, and blow hot air to a cooking chamber (not shown).

The coffee maker unit includes a case 131 at one side of the outfit room120, a water tank 132, a funnel 133, a water supply pipe 135, and aheater assembly 136.

The case 131 forms an exterior of the coffee maker unit, and the watertank 132 is at an upper portion of the case 121 for storing potablewater.

The funnel 133 under the water tank 132 has a filter (not shown) forextracting coffee. In more detail, the funnel 133 has a shape of a conehaving a great upper inside diameter, and a small lower inside diameter.On an inside of the funnel 133, there is a filter (not shown) of paperof non-woven fabric placed on an inside, on which coffee powder isfilled.

Therefore, when a hot potable water is supplied to the funnel 133, thecoffee powder is dissolved in the water, and coffee solution passesthrough the filter and drops downward. For this, under the funnel 133,there is a drop hole (not shown) in a bottom of the funnel 133 forenabling the coffee solution to drop downward.

In the meantime, under the funnel 133, there is a jug 134 as a containerfor storing coffee. The jug 134 has an opened top with a hand grip 134 aat one side.

Accordingly, by gripping the hand grip 134 a, the user can put the jug134 inside of the case 31, or take the jug 134 out of the case 131,easily. In general, the jug 134 is formed of transparent glass orplastic for the user to see a level of the coffee in the jug 134.

The water supply pipe 135 supplies the potable water from the water tank132 to the funnel 133. The water supply pipe 135 has one end connectedto the water tank 132, the other end positioned above the funnel 133,and a portion 135 a on a bottom of the case 131.

The heater assembly 136 is on the bottom of the case 131, and includes aheating heater 135 a, and a heat conservation heater 138.

During operation of the coffee maker unit 130, the heating heater 137heats the potable water being supplied to the funnel 133 along the watersupply pipe 135. The heat conservation heater 138 heats coffee in thejug 134, to maintain the coffee at a constant temperature. That is, theheat conservation heater 138 heats the jug 134 on the bottom of the case131 after extraction of coffee is finished, to maintain the extractedcoffee in a warm state.

Moreover, the heater assembly 136 is in contact with a portion 135 a ofthe water supply pipe 135 on the bottom of the case 131, and furtherincludes heater tube 139 having the heating heater 137 and the heatconservation heater 138 provided therein. Heat is transmitted from theheating heater 137 or the heat conservation heater 138 to the watersupply tube 135 and the jug 134 through the heater tube 139.

FIG. 3 illustrates a perspective view of a heater assembly in accordancewith a first preferred embodiment of the present invention, and FIG. 4illustrates a diagram showing detail of a heating heater and a heatconservation heater.

Referring to FIGS. 3 and 4, the heating heater 137 and the heatconservation heater 138 will be described in detail. The heating heater137 is constructed of a heating wire having about 750 W powerconsumption, and the heat conservation heater 138 is constructed of aheating wire having about 90 W power consumption.

There is a gap between the heating heater 137 and the heat conservationheater 138, for preventing short circuit caused by contact. In detail,the heating heater 137 is arranged in a helix around an axis of theheater tube 139, and the heat conservation heater 138 is arranged in ahelix along an inside circumferential surface of the heater tube 139.

The heating heater 137 and the heat conservation heater 138 haveinsulating portions 137 a, and 138 a at both ends, respectively. Theinsulating portions 137 a, and 138 a prevent the heating heater 137 andthe heat conservation heater 138 from coming into contact with eachother at portions thereof extended to an outside of the heater tube 139.

It is preferable that the insulating portion 137 a of the heating heater137 is extended longer than the insulating portion 138 a of the heatconservation heater 138 for preventing the heating heater 137 and theheat conservation heater 138 from coming into contact with each other,more positively.

In the meantime, the heater assembly 136 may be constructed of theheating heater 137 only. In this instance, the heating heater 137 notonly heats the potable water, but also conserves heat of the coffee inthe jug 134 after finish of the extraction of coffee, at the same time.

However, in this case, since conservation of heat of the coffee is madewith the heating heater 137 having a relatively higher powerconsumption, power is consumed unnecessarily. Particularly, when thecoffee maker is in operation together with the microwave oven, the powerconsumption increases excessively.

In more detail, presently, a standard upper limit value of a current tothe microwave oven is 15[A]. However, if conservation of heat of thecoffee is made with the heating heater 137, it is made known from a testthat a total current becomes 21[A] when the microwave oven unit and thecoffee maker unit are operated at the same time.

At the end, in order to meet the current upper limit, the microwave ovenunit and the coffee maker unit are operated, not at the same time, buteither one, selectively. Therefore, it is preferable that the heaterassembly 136 includes not only the heating heater 137, but also the heatconservation heater 138.

Thus, the first preferred embodiment of the present invention includesthe heat conservation heater 138 separately, for conservation of heat ofcoffee. According to this, unnecessary consumption of power can beprevented, to enable operation of the microwave oven unit and the coffeemaker unit at the same time.

In the meantime, if the user puts the coffee maker unit into operation,failing to know that, for an example, there is no water in the watertank 132 by mistake, the coffee maker and microwave oven in accordancewith a first preferred embodiment of the present invention may beinvolved in fire hazard and damage to the electric components caused byoverheating of the heating heater 137.

FIG. 5 illustrates a perspective view of a coffee maker and microwaveoven in accordance with a second preferred embodiment of the presentinvention.

Referring to FIG. 5, the coffee maker and microwave oven includes atemperature sensor 150 mounted on an outside surface of the heater tube139.

The temperature sensor 150 measures a temperature of the heating heater137 periodically. Then, the measured temperature value is provided to acontrol unit (not shown) for controlling operation of the coffee makerunit.

The control unit determines whether the heating heater 137 is overheatedor not according to the temperature value received. If it is determinedthat the heating heater 137 is overheated, power to the heating heater137 is cut off, to stop operation of the heating heater 137.

It is preferable that the temperature sensor includes a thermistor ofwhich internal resistance varies with a temperature.

Thus, since the temperature sensor 150 is provided, the coffee maker andmicrowave oven in accordance with a second preferred embodiment of thepresent invention can prevent problems caused by overheating of theheating heater 137.

FIG. 6 illustrates a section of a coffee maker and microwave oven inaccordance with a third preferred embodiment of the present invention,FIG. 7 illustrates a bottom perspective view of a coffee maker andmicrowave oven in accordance with a third preferred embodiment of thepresent invention, and FIG. 8 illustrates a bottom view of a coffeemaker and microwave oven in accordance with a third preferred embodimentof the present invention.

Referring to FIGS. 6 to 8, the coffee maker and microwave oven includesa case 231, a water tank 232, a funnel 233, a water supply pipe 235, anda heater assembly at one side of an outfit room 120 (see FIG. 1).

The case 231 forms an exterior of the coffee maker unit, and the watertank 232 is mounted on an upper space of the case 231, for storingpotable water.

Different from the first embodiment, the funnel 233 is at a center of aninside of the water tank 232. The positioning of the funnel 233 at aninside of the water tank 232 enables to provided more compact coffeemaker than that of the first embodiment which has spaces on upper sidesand lower sides of the water tank 232 and the funnel 233, respectively.

In the meantime, there is a jug 234 under the funnel 233 as a containerfor storing coffee. The jug 234 has a shape of a container having anopened top, with a hand grip 234 a at one side thereof.

The water supply pipe 235 supplies potable water from the water tank 232to the funnel 233. The water supply pipe 235 has one end connected tothe water tank 232, the other end positioned over the funnel 233, and aportion 235 a under the case 231. There is a shower head 235 b at theother end of the water supply pipe 235 for spraying potable water intoan inside of the funnel 233.

In the meantime, the heater assembly includes a heating heater 237, aheat conservation heater 238, both under the case 231.

The heating heater 237 heats potable water being supplied to the funnel233 along the water supply pipe 235 during operation of the coffee makerunit. The heat conservation heater 238 heats the coffee in the jug 234,to maintain the coffee at a constant temperature.

The heat assembly further includes a heater tube 239 in contact with theportion 235 a of the water supply pipe 235 under the case 231. Theheating heater 237 is inside of the heater tube 239.

The heating heater 237 has first terminals 237 a at both ends of theheating heater 237, connected to a coil (not shown) which suppliespower.

It is preferable that the heating heater 237 includes a sheath heaterhaving about 750 W of power consumption. As the sheath heater is a kindof heater used widely, a detailed description of which will be omitted.

The heat conservation heater 238 is on an opposite side of the heatingheater 237 with respect to the portion 235 a of the water supply pipe235 under the case 231.

It is preferable that the heat conservation heater 238 includes a plateheater in close contact with an underside of the case 231, to supplyheat to the jug 234, uniformly.

At one side of an underside of the heat conservation heater 238, thereis a second terminal 238 a connected to the coil 240 for supplyingpower.

The heat conservation heater 238 has about 90 W of power consumption,for enabling use of the microwave oven unit even during operation of theheat conservation heater 238 like the first embodiment.

In the meantime, on an underside of the case 31, there is a heatconduction plate 241 of good thermal conductivity for effectivetransmission of heat from the heat conservation heater 238 to the jug234.

In this instance, the portion 235 a of the water supply pipe 235, andthe heater tube 239 is provided on an underside of the heat conductionplate 241, particularly, the heat conservation heater 238 is in closecontact with the heat conduction plate 241.

In the meantime, it is preferable that the heat conservation heater 238is enclosed with a metal plate 242 having a good thermal conductivityexcept the portion of the second terminal 238 a. The metal plate 242prevents the heat conservation heater 238 from being in direct contactwith the underside of the case 231, and enables fast transmission ofheat from the heat conservation heater 238 to the jug 234.

However, if the heat conservation heater 238 is enclosed with the metalplate 242, the second terminal 238 a is liable to contact with the metalplate 242. Therefore, the second terminal 238 a is provided with aninsulating portion 243.

The insulating portion 243 prevents the second terminal 238 a from beingbrought into contact with the metal plate 242 when the second terminal238 a bent to one side. In more detail, it is preferable that theinsulating portion 243 is formed of an insulating material, such assilicon.

On a front of the case 231, there is a door panel 246 of the cabinet 100(see FIG. 1) mounted thereon. In general, the door panel 246 is formedof ABS resin (Acrylonitrile Butadiene Styrene Copolymer), and has aportion under the heat conservation heater 238.

Therefore, when the heat conservation heater 238 starts to operate, theportion of the door panel 246 under the heat conservation heater 238 isliable to suffer from damage caused by heat. In order to prevent this,on an underside of the heat conservation heater 238, there is ashielding plate 247 for shielding the heat from the heat conservationheater 238.

Of course, in a case the heat conservation heater 238 is enclosed withthe metal plate 242, the shielding plate 247 is placed on an undersideof the metal plate 242.

FIG. 9 illustrates a partial side section of a coffee maker andmicrowave oven in accordance with a third preferred embodiment of thepresent invention.

In the meantime, referring to FIG. 9, around the second terminal 238 aconnected to the coil 240, there are at least two conductive wires woundthereon, for enlarging a surface area of the second terminal 238 a, toreduce a resistance thereof.

In more detail, if a current flows to the second terminal 238 a throughthe coil 240, there is an induced electromotive force generated at aninside of the second terminal 238 a that impedes flow of the current.The induced electromotive force increases an internal resistance of thesecond terminal 238 a, to overheat the second terminal 238 a.

This is called as a skin effect, and the conductive wires 244, woundaround the second terminal 238 a to increase a surface area of thesecond terminal 238 a, decreases the skin effect. That is, theconductive wires 244 reduce the resistance of the second terminal 238 a,to make a current flow smooth.

The conductive wires 244 are connected to the coil 240. According tothis, a connection portion of the second terminal 238 a and the coil240, which is relatively weak to an external force, is reinforced by theconductive wires 244, to prevent the connection portion of the secondterminal 238 a and the coil 240 from breaking, easily.

It is preferable that an insulating tube 245 is provided to theconnection portion between the conductive wires 244 and the coil 240.The insulating tube 245 surrounds the connection portion between theconductive wires 244 and the coil 240, for protecting the connectionportion from an external force, and improving an insulating performance.

In detail, the insulating tube 245 is formed of an insulating material,such as silicon rubber.

Thus, alike the first embodiment, the coffee maker and microwave oven inaccordance with the third preferred embodiment of the present inventionpermits simultaneous operation of the coffee maker unit and themicrowave oven unit by providing the heating heater 237, and the heatconservation heater 238.

Moreover, by using a plate heater as the heat conservation heater 238for improving thermal conductivity, and by providing a heat conductionplate 241 to be in close contact with the plate heater on the undersideof the case 231, smooth heat conservation of the coffee is made possiblewith a low power consumption.

Furthermore, alike the second embodiment, the coffee maker and microwaveoven in accordance with the third preferred embodiment of the presentinvention may includes a temperature sensor 150 (see FIG. 5) forpreventing the heating heater 237 from overheating.

Methods for controlling a coffee maker and microwave oven in accordancewith the foregoing embodiments of the present invention will bedescribed.

FIG. 10 illustrates a flow chart showing the steps of a method forcontrolling a coffee maker and microwave oven in accordance with afourth preferred embodiment of the present invention.

Referring to FIG. 10, the control unit determines whether a coffeeextraction order for the coffee maker unit is received from a user ornot (S100). In general, the coffee extraction order is applied to a keypanel (not shown) on a front of the microwave oven unit.

As a result of the determination (S100), if the coffee extraction orderis received from the user, potable water is supplied to a funnel 133, or233 through a water supply pipe 135, or 235, and, at the same time withthis, a heating heater is put into operation, to heat the potable water(S110).

In this instance, the potable water is heated with the heating heater137 or 237 in a course the potable water is supplied to the funnel 233.The coffee is extracted by the heated potable water at the funnel 133 or233 (S120).

During above steps (S100˜S120) are progressed, the control unit countsan operation time period of the heating heater 137, or 237, and comparesthe operation time period of the heating heater 137, or 237 to a presettime period (S130) (S140).

For this, the control unit has a timer for counting the operation timeperiod of the heating heater 137 or 237, and a memory for storing thepreset time period.

The preset time period is a maximum time period required starting fromapplication of the coffee extraction order by the user to extraction ofcoffee, determined by test at the time of production.

That is, the preset time period is a maximum operation time period ofthe heating heater 137 or 237 for extraction of the coffee. Therefore,the preset time period varies with a capacity of the coffee maker unit,and the like.

As a result of the determination (S140), if the operation time period ofthe heating heater 137, or 237 does not exceed the preset time period,the heating heater 137 or 237 is kept operation, to keep extraction ofcoffee.

On the other hand, as the result of the determination (S140), if theoperation time period of the heating heater 137, or 237 exceeds thepreset time period, the heating heater 137 or 237 is stopped, and theheat conservation heater 138 or 238 is put into operation, to maintain atemperature of the extracted coffee (S150) (S160).

Accordingly, though extraction of coffee is performed by the heatingheater 137, or 237, conservation of heat of the extracted coffee havingextraction of coffee finished is performed by the heat conservationheater 138, or 238.

Thus, in the fourth embodiment, if the operation time period of theheating heater 137 or 237 exceeds the preset time period, the controlunit stops the heating heater 137 or 237, to prevent a problem caused byoverheating of the heating heater 137 or 237 from occurring in advance.

Moreover, the conservation of heat of the extracted coffee is performedby the heat conservation heater 138, or 238 having a power consumptionrelatively lower than the heating heater 137 or 237, the coffee makerunit and the microwave oven unit can be operated at the same time.

FIG. 11 illustrates a flow chart showing the steps of a method forcontrolling a coffee maker and microwave oven in accordance with a fifthpreferred embodiment of the present invention.

Referring to FIG. 11, a control unit determines whether a coffeeextraction order is received from a user or not (S200). In general, thecoffee extraction order is applied to a key panel (not shown) on a frontof the microwave oven unit.

As a result of determination (S200), if the coffee extraction order isreceived, potable water is supplied to the funnel 133, or 233, and, atthe same time with this, the heating heater 137, or 237 is put intooperation, to heat the potable water (S210).

Then, the temperature sensor 150 measures a temperature T of the heatingheater 137, or 237 periodically (S220). The control unit receives thetemperature T having the temperature sensor 150 sensed, and calculates arate ΔT of temperature change of the heating heater 137, or 237 (S230).

The rate of temperature change of the heating heater 137 or 237 iscalculated according to the following equation.ΔT=(T _(n) −T _(n−1))/(t _(n) −t _(n−1))

Where, ΔT denotes a rate of temperature change of the heater, T_(n)denotes the heating heater temperature measured at a t_(n) time, andT_(n−1) denotes the heating heater temperature measured at a t_(n−1)time.

Then, the control unit determines whether the rate ΔT of temperaturechange calculated is lower than a preset value (S240).

If the rate ΔT of temperature change calculated is lower than a presetvalue, the heat conservation heater 138, or 238 is operated togetherwith the heating heater 137, or 237, to extract coffee (S250) (S260).

The preset value is a very small value close to ‘0’ stored in the memoryof the control unit.

In more detail, the heating heater 137, or 237 has a temperature whichrises rapidly at the same time of starting the heating heater 137, or237 for heating the potable water. If there is an adequate rate ofpotable water flow to the funnel 133, or 233 along the water supply pipe135, or 235, the temperature of the heating heater 137, or 237 rises nomore, but maintains a fixed value.

At a time point the heating heater 137, or 237 starts to maintain thefixed temperature, i.e., the rate ΔT of temperature change being ‘0’,the heat conservation heater 520 is put into operation. Therefore, thepreset value, which is to be compared to the rate ΔT of temperaturechange of the heating heater 137, or 237, is set to be a value veryclose to ‘0’.

In the meantime, as described before, when the heating heater 137, or237 and the heat conservation heater 138, or 238 are operated together,the potable water passing through the water supply pipe 135 is heatedmore quickly, before being supplied to the funnel 133, or 233.

Accordingly, if the heating heater 137, or 237 and the heat conservationheater 138, or 238 are operated together, a time period required forextraction of coffee can be shortened compared to a case when only theheating heater 137, or 237 is operated.

Thereafter, if it is determined that extraction of coffee is finished,the heating heater 510 is stopped (S270, S280). The finish of theextraction of coffee is determined according to the temperature of theheating heater 137, or 237 measured at the temperature sensor 150.

In more detail, if the extraction of coffee is progressed for more thana preset time period, the temperature of the heating heater 137, or 237,having being at a fixed temperature, rises sharply. This is because theheating heater 137, or 237 is overheated due to shortage of potablewater supplied to the funnel 133, or 233 through the water supply tube135, or 235 as the extraction of coffee is progressed.

In this instance, determining that there is no potable water in thewater tank 132, or 232 for extraction of coffee if the temperature ofthe heating heater 137, or 237 rises over a preset temperature, thecontrol unit stops operation of the heating heater 137, or 237.

That is, the control unit, determining that the extraction of coffee isfinished, stops the operation of the heating heater 137, or 237. In thisinstance, the heat conservation heater 138, or 238 is not stopped, butkept operated to maintain a temperature of the coffee in the jug 34(290).

By extracting coffee both with the heating heater 137, or 237, and theheat conservation heater 138, or 238 operated at the same time, thefifth embodiment of the present invention shortens a time periodrequired for extracting coffee.

Moreover, by stopping operation of the heating heater 137, or 237determining that extraction of coffee is finished if the temperature ofthe heating heater 137, or 237 rises to a temperature higher than apreset temperature, the problem caused by overheating of the heatingheater 137, or 237 is prevented.

FIG. 12 illustrates a flow chart showing the steps of a method forcontrolling a coffee maker and microwave oven in accordance with a sixthpreferred embodiment of the present invention.

Referring to FIG. 12, a control unit of the coffee maker and microwaveoven determines whether a coffee extraction order is received from auser or not (S300). In general, the coffee extraction order is appliedto a key panel (not shown) on a front of the microwave oven unit.

As a result of determination (S300), if the coffee extraction order isreceived, potable water is supplied to the funnel 133, or 233, and, atthe same time with this, the heating heater 137, or 237 is put intooperation (S310).

In this instance, the potable water is heated by the heating heater 137,or 237 in a course the potable water is supplied to the funnel 133, or233. The heated potable water extracts coffee at the funnel 133, or 233(S320).

Then, the temperature sensor 150 measures a temperature T of the heatingheater 137, or 237 periodically (S330). The control unit receives thetemperature T having the temperature sensor 150 sensed, and calculates arate ΔT of temperature change of the heating heater 137, or 237 (S340).

The rate of temperature change of the heating heater 137 or 237 iscalculated according to the following equation.ΔT=(T _(n) −T _(n−1))/(t _(n) −t _(n−1))

Where, ΔT denotes a rate of temperature change of the heater, T_(n)denotes the heating heater temperature measured at a t_(n) time, andT_(n−1) denotes the heating heater temperature measured at a t_(n−1)time.

Then, the control unit determines whether the rate ΔT of temperaturechange exceeds a preset value (S340).

Determining that extraction of coffee is finished if the rate ΔT oftemperature change exceeds the preset value, the heating heater 137, or237 is stopped, and the heat conservation heater 150 is operated (S350)(S360).

That is, if the temperature of the heating heater 137, or 237 risessharply such that the rate of temperature change is higher than a presetvalue, determining that extraction of coffee is finished, and no morepotable water is supplied to the funnel 133, or 233, the heating heater137, or 237 is stopped, and the heat conservation heater 138, or 238 isoperated.

In this instance, the heat conservation heater 138, or 238 is operatedfor a preset heat conservation time period. When an operation timeperiod of the heat conservation heater 138, or 238 passes the presetheat conservation time period, the heat conservation heater 138, or 238is stopped, to terminate the heat conservation (S370) (S380).

Of course, if the operation time period of the heat conservation heater138, or 238 does not exceed the preset heat conservation time period,the heat conservation heater 138, or 238 is kept operated, to maintainthe temperature of the coffee.

On the other hand, if operation of the heat conservation heater 138, or238 is stopped, the temperature of coffee in the jug 134, or 234 dropsas time passes by.

In this instance, if a coffee temperature conservation order is receivedfrom the user (S390), the coffee conservation heater 138, or 238 is putinto operation again, to conserve the temperature of the coffee, again.

It is preferable that a separate key is provided to the key panel thecoffee extraction order is to be applied thereto, for application of thecoffee temperature conservation order.

The sixth embodiment of the present invention permits to put the heatconservation heater 138, or 238 into operation any time according toorder of the user even if operation of the coffee maker unit is stoppedafter extraction of coffee, to conserve the heat of the coffee in thejug 133, 233. According to this, the user can use the coffee maker unitmore effectively.

As has been described, the coffee maker and microwave oven and methodfor controlling the same of the present invention have the followingadvantages.

The heating heater 137, or 237 and the heat conservation heater 138, or238 provided separately for extraction of coffee and conservation ofcoffee temperature permit simultaneous use of the coffee maker unit andmicrowave oven unit.

The temperature sensor or the control method for preventing the heatingheater 137, or 237 from overheating permits to have a plurality ofadditional advantages described above.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the present inventionwithout departing from the spirit or scope of the inventions. Thus, itis intended that the present invention covers the modifications andvariations of this invention provided they come within the scope of theappended claims and their equivalents.

1. A coffee maker and microwave oven comprising: a microwave generator for generating a microwave; a cooking chamber for cooking food using the microwave transmitted to the cooking chamber; an outfit room for mounting electric components therein; a case in the outfit room; a water tank in the case; a funnel in the case and having a filter placed thereon for extracting coffee; a jug under the funnel for storing the extracted coffee; a water supply pipe having a first end connected to the water tank, a second end located over the funnel, and a portion on a bottom of the case; and a heater assembly on the bottom of the case, the heater assembly having a heating heater for heating water passing through the water supply pipe, and a heat conservation heater for heating coffee in the jug to maintain a temperature of the coffee constant.
 2. The coffee maker and microwave oven as claimed in claim 1, wherein the heater assembly further includes a heater tube in contact with the water supply pipe on the bottom of the case, the heating heater and the heat conservation heater being mounted in the heater tube.
 3. The coffee maker and microwave oven as claimed in claim 2, wherein the heating heater includes a heating wire with a 750 W power consumption, and the heat conservation heater includes a heating wire with a 90 W power consumption.
 4. The coffee maker and microwave oven as claimed in claim 3, wherein the heating heater has a fixed gap to the heat conservation heater.
 5. The coffee maker and microwave oven as claimed in claim 4, wherein the heating heater is wound around an axis of the heater tube in a helix, and the heat conservation heater is wound along an inside circumferential surface of the heater tube in a helix.
 6. The coffee maker and microwave oven as claimed in claim 3, wherein the heating heater and the heat conservation heater include insulating portion at both ends respectively, for preventing short circuit.
 7. The coffee maker and microwave oven as claimed in claim 6, wherein the insulating portion of the heating heater is longer than the insulating portion of the heat conservation heater.
 8. The coffee maker and microwave oven as claimed in claim 2, further comprising a temperature sensor on an outside surface of the heater tube for measuring a temperature of the heating heater.
 9. The coffee maker and microwave oven as claimed in claim 8, wherein the temperature sensor includes a thermistor of which internal resistance varies with a temperature.
 10. The coffee maker and microwave oven as claimed in claim 1, wherein the funnel is at a center of an inside of the water tank.
 11. The coffee maker and microwave oven as claimed in claim 10, wherein the water pipe includes a shower head at the other end thereof over the funnel for spraying potable water into an inside of the funnel.
 12. The coffee maker and microwave oven as claimed in claim 1, wherein the heater assembly further includes a heater tube in contact with the portion of the water supply pipe on the bottom of the case, the heating heater being located in the heater tube.
 13. The coffee maker and microwave oven as claimed in claim 12, wherein the heating heater includes first terminals at both ends respectively connected to a coil for supplying power.
 14. The coffee maker and microwave oven as claimed in claim 12, wherein the heating heater includes a sheath heater.
 15. The coffee maker and microwave oven as claimed in claim 12, wherein the heat conservation heater is positioned opposite to the heating heater with respect to the portion of the water supply tube on the bottom of the case.
 16. The coffee maker and microwave oven as claimed in claim 12, wherein the heat conservation heater includes a plate heater in close contact with an underside of the case.
 17. The coffee maker and microwave oven as claimed in claim 16, wherein the heat conservation heater includes a second terminal on one side of an underside thereof connected to a coil for supplying power thereto.
 18. The coffee maker and microwave oven as claimed in claim 17, wherein the heat conservation heater is enclosed with a metal plate having a good thermal conductivity excluding a portion having the second terminal formed thereon.
 19. The coffee maker and microwave oven as claimed in claim 12, further comprising a heat conduction plate on an underside of the case for effective transmission of heat from the heat conservation heater to the jug, and the heat conservation heater is in close contact with an underside surface of the heat conduction plate.
 20. The coffee maker and microwave oven as claimed in claim 16, wherein the case further includes a door panel on a front of the case, having a portion positioned below the heat conservation heater, and the heat conservation heater includes a shielding plate on an underside of the heat conservation heater for preventing transmission of heat from the heat conservation heater to the door panel.
 21. The coffee maker and microwave oven as claimed in claim 17, wherein the second terminal includes at least two conductive wires wound around the second terminal and connected to the coil.
 22. The coffee maker and microwave oven as claimed in claim 21, wherein the connection portion of the conductive wires and the coil further includes an insulating tube. 